The invention relates to an apparatus on a spinning preparation machine, especially a flat card, roller card or the like, in which at least one clothed and/or non-clothed, basically stationary machine element lies opposite and spaced apart from the clothing of a roller, for example a cylinder.
In certain known arrangements the bearing surfaces of the end portions of the machine element are in engagement with respective bearing surfaces of stationary bearings and there are arranged in the region of each of the end portions and the bearings an adjustment means which is able to alter the radial spacing between the clothing of the roller and the machine element.
The spacings between the cylinder clothing and surfaces lying opposite the cylinder clothing (counter-surfaces) are of major importance for the technical characteristics of the machinery and fibres. The carding result, that is to say in terms of cleaning, nep formation and fibre shortening, is substantially dependent upon the carding nip, that is to say the spacing between the cylinder clothing and the clothings of the revolving and fixed card tops. Guiding air around the cylinder and directing away heat are likewise dependent upon the spacing between the cylinder clothing and clothed or non-clothed surfaces lying opposite, for example take-off blades or casing elements. The spacings are subject to a variety of influences, some of which act counter to one another. The wear to clothings lying opposite one another results in an increase in the size of the carding nip, which is associated with a rise in the number of neps and with a reduction in fibre shortening. Increasing the speed of rotation of the cylinder, for example in order to enhance the cleaning action, entails expansion of the cylinder, including the clothing, as a result of centrifugal force and, consequently, brings about a reduction in the size of the carding nip. Also, during the processing of large amounts of fibre and certain kinds of fibre, for example synthetic fibres, as a result of a rise in temperature the cylinder expands to a greater extent than does the rest of the surrounding machinery, so that the spacings become smaller for that reason also. The machine elements lying radially opposite the cylinder, for example fixed carding segments and/or take-off blades, also expand.
The carding nip is affected especially by the machine settings on the one hand and by the condition of the clothing on the other hand. The most important carding nip of the revolving card top carding machine is located in the main carding zone, that is to say between the cylinder and the revolving card top assembly. At least one clothing which limits the working spacing of the carding zone as a whole is in motion. In order to increase the production rate of the carding machine, it is sought to select an operating rotational speed, i.e. the operating speed of the moving parts, that is as high as fibre processing technology allows. The working spacing is effected in the radial direction (starting from the rotational axis) of the cylinder.
During carding, increasingly large amounts of fibre material are processed per unit of time, which requires higher working component speeds and higher outputs. The increasing throughput of fibre material (production rate), even when the working surface area remains constant, results in increased generation of heat as a result of the mechanical work. At the same time, however, the technological carding result (sliver uniformity, degree of cleaning, nep reduction etc.) is constantly being improved, which requires a greater number of effective surfaces in carding engagement and narrower settings of those effective surfaces with respect to the cylinder (tambour). The proportion of synthetic fibres being processed, which—compared with cotton—generate more heat as a result of friction when in contact with the effective surfaces of the machine, is continually increasing. The working components of high performance carding machines are nowadays totally enclosed on all sides in order to conform to the high safety standards, to prevent the emission of particles into the spinning room environment and to minimise the need for servicing of the machines. Grids or even open, material-guiding surfaces allowing exchange of air are a thing of the past. The said circumstances markedly increase the input of heat into the machine, while the discharge of heat by means of convection is markedly reduced. The resulting more intense heating of high performance carding machines leads to greater thermoelastic deformation which, on account of the non-uniform distribution of the temperature field, affects the set spacings of the effective surfaces: the gaps between cylinder and card top, doffer, fixed card tops and take-off stations having blades are reduced. In an extreme case, the set gap between the effective surfaces can be completely consumed by thermal expansion, so that components moving relative to one another collide, resulting in considerable damage to the affected high performance carding machine. Accordingly, particularly the generation of heat in the working region of the carding machine can lead to different degrees of thermal expansion when the temperature differences between the components are too great.
In a known apparatus (EP 0 422 838) the cylinder of a carding machine is associated with a plurality of stationary carding segments (fixed carding segments) each of which is attached by way of its end portions to the associated side frame of the carding machine. On each end face of each carding segment there is a plate having a lug towards the outside, on which a fixing screw having an adjustment nut is mounted. By manual operation of the adjustment nut, the radial spacing of the clothing of the carding segment with respect to the cylinder clothing can be adjusted individually. The adjustment operation by way of the adjustment nuts for the purpose of obtaining a desired and uniform carding nip at the beginning of assembly or in the event of readjustment is complicated. Adjustment can be made only with the machine at a standstill with the result that, in addition, the ongoing production operation of the carding machine is interrupted.
It is an aim of the invention to provide an apparatus of the kind described at the beginning which avoids or mitigates the mentioned disadvantages, which is especially simple in terms of structure and assembly and which enables the carding nip to be adapted or kept constant in the event of thermally induced changes in the dimensions of the machine element and/or the roller, especially during ongoing operation.